1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: DTV.fe
3
4.. _FE_SET_VOLTAGE:
5
6********************
7ioctl FE_SET_VOLTAGE
8********************
9
10Name
11====
12
13FE_SET_VOLTAGE - Allow setting the DC level sent to the antenna subsystem.
14
15Synopsis
16========
17
18.. c:macro:: FE_SET_VOLTAGE
19
20``int ioctl(int fd, FE_SET_VOLTAGE, enum fe_sec_voltage voltage)``
21
22Arguments
23=========
24
25``fd``
26    File descriptor returned by :c:func:`open()`.
27
28``voltage``
29    an integer enumered value described at :c:type:`fe_sec_voltage`
30
31Description
32===========
33
34This ioctl allows to set the DC voltage level sent through the antenna
35cable to 13V, 18V or off.
36
37Usually, a satellite antenna subsystems require that the digital TV
38device to send a DC voltage to feed power to the LNBf. Depending on the
39LNBf type, the polarization or the intermediate frequency (IF) of the
40LNBf can controlled by the voltage level. Other devices (for example,
41the ones that implement DISEqC and multipoint LNBf's don't need to
42control the voltage level, provided that either 13V or 18V is sent to
43power up the LNBf.
44
45.. attention:: if more than one device is connected to the same antenna,
46   setting a voltage level may interfere on other devices, as they may lose
47   the capability of setting polarization or IF. So, on those cases, setting
48   the voltage to SEC_VOLTAGE_OFF while the device is not is used is
49   recommended.
50
51Return Value
52============
53
54On success 0 is returned.
55
56On error -1 is returned, and the ``errno`` variable is set
57appropriately.
58
59Generic error codes are described at the
60:ref:`Generic Error Codes <gen-errors>` chapter.
61